Carbon nanotubes - curse or blessing.

Although nanotechnology is a relatively new scientific field, quite many different products are already introduced in the market containing nanosized particles. A special class of nanosized materials namely the carbon nanotubes (CNT) possesses outstanding new properties and extraordinary potential for creating new products. Carbon nanotubes are already used in various consumer products, industrial applications and science. It is not as this time clear how CNT are able to affect human health since most types of CNTs differ significantly in terms of structural characteristics (morphology, size, shape and length), surface properties (surface chemistry and surface charge) and chemical composition. This review provides an overview about contradicting reports that are found in the literature. We summarize the studies that report about nontoxic as well as toxic effects of CNT in-vitro and in-vivo. We describe how carbon nanotubes can readily be degraded under certain conditions. Another phenomenon is that despite the observed toxic effects which may occur to cells, organs and animals after uptake of CNT, intensive research investigations were undertaken in order to use these outstanding materials in medical applications. The second part of this review starts with a short description of the main principles in metrology. Observed conflicts were discussed in CNT toxicity assays into terms of measurement science or metrology issues. It was demonstrated that any specification of a measurand is only valid within the given framework. This means that many of the published results are within their measurement framework correct, but there are no means to compare them outside this framework.

Investigating cell-material interactions by monitoring and analysing cell migration.

Cell-material interactions can on one hand be characterised by assessing the functional state and or shape of the cells at one or different discrete periods of time, on the other hand by observing cell migration and spreading behaviour. The object of this study was to investigate the migration behaviour of fluorescently labelled cells, and to evaluate the software analysing this migration. In the present study, the behaviour of fibroblasts cells on differently structured surfaces was taken as example. In the first step, the influence of seven different lipophilic dyes (Dil, DiO, DiA, DiD, DiR, PKH2 and PKH26) on cell performance was determined taking biochemical parameters as indices. In the second step, the fluorescence characteristics of these dyes were compared regarding their applicability. In the third step, migration behaviour of Dil-labelled fibroblastic cells on plane and grooved surfaces were monitored and analysed using specific software. Our data suggest that most of the dyes have optimal characteristics for studying cell-cell interactions. Cell migration behaviour regarding migration direction and cell spreading was different on plane and grooved surfaces. It could be shown that computer-based image analysis represents a practical, quick and objective tool to quantify exactly cell migration behaviour.

Transformation of 3- and 4-Picoline under Sulfate-Reducing Conditions.

A microbial population which transformed 3- and 4-picoline under sulfate-reducing conditions was isolated from a subsurface soil which had been previously exposed to different N-substituted aromatic compounds for several years. In the presence of sulfate, the microbial culture transformed 3- and 4-picoline (0.4 mM) within 30 days. From the amounts of ammonia released and of sulfide that were determined during the transformation of 3-picoline, it can be concluded that the parent compound was mineralized to carbon dioxide and ammonia. During the transformation of 4-picoline, a UV-absorbing intermediate accumulated in the culture medium. This metabolite was identified as 2-hydroxy-4-picoline by gas chromatography-mass spectrometry and nuclear magnetic resonance analysis, and its further transformation was detected only after an additional month of incubation. The small amount of sulfide produced during the oxidation of 4-picoline and the generation of the hydroxylated metabolite indicated that the initial step in the metabolic pathway of 4-picoline was a monohydroxylation at position 2 of the heterocyclic aromatic ring. The 3- and 4-picoline-degrading cultures could also transform benzoic acid; however, the other methylated pyridine derivatives, 2-picoline, dimethyl-pyridines, and trimethylpyridines, were not degraded.

Microbial transformation of heterocyclic molecules in deep subsurface sediments.

Recently attempts have been made to establish the presence and to determine the metabolic versatility of microorganisms in the terrestrial deep subsurface at the Savannah River Plant, Aiken, SC, USA. Sediment samples obtained at 20 different depths of up to 526 m were examined to determine carbon mineralization under aerobic, sulfate-reducing, and methanogenic conditions. The evolution of(14)CO2 from radiolabelled glucose was observed under aerobic conditions in all sediments, whereas pyridine was transformed in 50% of the 20 sediments and indole was metabolized in 85% of the sediments. Glucose mineralization in certain sediments was comparable to that in the surface environment. Sulfate was reduced in only five sediments, and two were carbon limited. Methane production was detected in ten sediments amended with formate only after long-term incubations. The transformation of indole and pyridine was only rarely observed under sulfate-reducing conditions and was never detected in methanogenic incubations. This study provides information concerning the metabolic capability of both aerobic and anaerobic microorganisms in the deep subsurface and may prove useful in determining the feasibility of microbial decontamination of such environments.

Microbial metabolism of pyridine, quinoline, acridine, and their derivatives under aerobic and anaerobic conditions.

Our review of the metabolic pathways of pyridines and aza-arenes showed that biodegradation of heterocyclic aromatic compounds occurs under both aerobic and anaerobic conditions. Depending upon the environmental conditions, different types of bacteria, fungi, and enzymes are involved in the degradation process of these compounds. Our review indicated that different organisms are using different pathways to biotransform a substrate. Our review also showed that the transformation rate of the pyridine derivatives is dependent on the substituents. For example, pyridine carboxylic acids have the highest transformation rate followed by mono-hydroxypyridines, methylpyridines, aminopyridines, and halogenated pyridines. Through the isolation of metabolites, it was possible to demonstrate the mineralization pathway of various heterocyclic aromatic compounds. By using 14C-labeled substrates, it was possible to show that ring fission of a specific heterocyclic compound occurs at a specific position of the ring. Furthermore, many researchers have been able to isolate and characterize the microorganisms or even the enzymes involved in the transformation of these compounds or their derivatives. In studies involving 18O labeling as well as the use of cofactors and coenzymes, it was possible to prove that specific enzymes (e.g., mono- or dioxygenases) are involved in a particular degradation step. By using H2 18O, it could be shown that in certain transformation reactions, the oxygen was derived from water and that therefore these reactions might also occur under anaerobic conditions.

Different handling of beta 2-microglobulin during hemodialysis and hemofiltration.

Very recently it was reported that the amyloid associated with chronic hemodialysis contains, as a major component, a new form of amyloid fibril protein which is homologous to beta 2-microglobulin. As beta 2-microglobulin has a molecular weight of 11,600 daltons, investigations were carried out to see whether or not this protein would be handled differently by hemodialysis and hemofiltration, because the latter method especially is capable of eliminating solutes with such a high molecular weight. The results clearly indicate that hemofiltration removes substantial amounts of beta 2-microglobulin (about 190 mg per treatment, which represents 80% of daily production). It remains to be clarified whether or not hemofiltration is therefore superior to hemodialysis with regard to amyloid deposit formation.

Significant reduction of factor D and immunosuppressive complement fragment Ba by hemofiltration.

Because of their effect on the immune response, especially in patients with chronic or acute renal failure, factor D (FD) and the immunosuppressive complement fragment Ba are substances which may be important for the immunological status. Since they cannot be eliminated by conventional Cuprophan hemodialysis because of their high molecular weight (24,000 and 33,000 D, respectively), the effect of hemofiltration (HF) on the plasma concentration of both components was tested. It was shown that plasma levels of FD can be lowered by 43.5% during an HF treatment and the plasma concentration of Ba by 30.6%. Moreover, the two substances could be detected in the hemofiltrate. Up to 75 mg FD and up to 37 mg Ba could be eliminated per treatment, depending on the plasma concentrations and the filtration volume. A convective method such as chronic HF is therefore clearly superior to diffusive methods of blood purification when substances with such a high molecular weight have to be eliminated. It has still to be established whether the elimination of FD and Ba by chronic intermittent HF results in a sustained improvement in the immunological status of patients treated in this way.